Stent for the positioning and anchoring of a valvular prosthesis in an implantation site in the heart of a patient

ABSTRACT

The present invention relates to a stent ( 10 ) for the positioning and anchoring of a valvular prosthesis ( 100 ) in an implantation site in the heart of a patient. Specifically, the present invention relates to an expandable stent for an endoprosthesis used in the treatment of a narrowing of a cardiac valve and/or a cardiac valve insufficiency. So as to ensure that no longitudinal displacement of a valvular prosthesis ( 100 ) fastened to a stent ( 10 ) will occur relative the stent ( 10 ) in the implanted state of the stent ( 10 ), even given the peristaltic motion of the heart, the stent ( 10 ) according to the invention comprises at least one fastening portion ( 11 ) via which the valvular prosthesis ( 100 ) is connectable to the stent ( 10 ). The stent ( 10 ) further comprises positioning arches ( 15 ) and retaining arches ( 16 ), whereby at least one positioning arch ( 15 ) is connected to at least one retaining arch ( 16 ) via a first connecting land ( 17 ). The stent ( 10 ) moreover comprises at least one auxiliary retaining arch ( 18 ) which connects the respective arms ( 16′, 16 ″) of the at least one retaining arch ( 16 ) connected to the at least one positioning arch ( 15 ).

The present invention relates to a stent for the positioning andanchoring of a valvular prosthesis in an implantation site in the heartof a patient. Specifically, the present invention relates to anexpandable stent for an endoprosthesis used in the treatment of astenosis (narrowing) of a cardiac valve and/or a cardiac valveinsufficiency.

The expression “narrowing (stenosis) of a cardiac valve and/or cardiacvalve insufficiency” is intended to include a functional defect of oneor more cardiac valves, which is either genetic or has developed. Acardiac defect of this type might affect each of the four heart valves,although the valves in the left ventricle (aortal and mitral valves) areaffected much more often than the right-sided part of the heart(pulmonary and tricuspid valves). The functional defect can result innarrowing (stenosis), inability to close (insufficiency) or acombination of the two (combined vitium). This invention relates to anexpandable stent for inserting a heart valve stent in a patient's bodyfor treating such a heart valve defect.

In the current treatment of severe narrowing of a cardiac valve and/orcardiac valve insufficiency, the narrowed or diseased cardiac valve isreplaced with a valvular prosthesis. Biological or mechanical valvesmodels, which are typically surgically sewn into the cardiac valve bedthrough an opening in the chest after removal of the diseased cardiacvalve, are used for this purpose. This operation necessitates the use ofa heart-lung machine to maintain the patient's circulation during theprocedure and cardiac arrest is induced during implantation of theprosthesis. This is a risky surgical procedure with associated dangersfor the patient, as well as a long post-operative treatment and recoveryphase. Such an operation can often not be considered with justifiablerisk in the case of polypathic patients.

Minimally-invasive forms of treatment have been developed recently whichare characterized by allowing the procedure to be performed under localanesthesia. One approach provides for the use of a catheter system toimplant a self-expandable stent to which is connected a collapsiblevalvular prosthesis. Such a self-expandable endoprothesis can be guidedvia a catheter system to the implantation site within the heart throughan inguinal artery or vein. After reaching the implantation site, thestent can then be unfolded.

To this end, it is known that a stent may be comprised of, for example,a plurality of self-expanding longitudinal stent segments, the segmentsbeing articulated relative one another. In order to anchor the stentsecurely in position the an appropriate blood vessel close to the heart,anchoring barbs are frequently used to engage with the vascular wall.

An expandable stent for the fastening and anchoring of a valvularprosthesis is known from printed publication DE 10 010 074 A1, wherebythe stent is essentially formed of wire-shaped, interconnected segments.DE 10 010 074 A1 proposes a stent for fastening and anchoring a valvularprosthesis, the stent having different arched elements which assume thefunction of fastening and supporting the valvular prosthesis at the siteof implantation. Specifically, three identically-configured positioningarches spaced 120° from one another respectively are used. Thesepositioning arches are connected to one another by means of solid bodyarticulations. Addition to the positioning arches, complementary curvedretaining arches serve to anchor the endoprothesis by pressing radiallyagainst the vascular wall following the unfolding of the stent.

However, there is a risk of inexact or incorrect implantation of avalvular prosthesis using the solutions described above. Expressed inanother way. There is a need for exact positioning and longitudinalalignment of an implanted valvular prosthesis. In particular, it is onlypossible using great skill on the part of the attending surgeon orcardiologist—if at all—to position a stent sufficiently precisely, inboth a lateral and longitudinal direction, to ensure that the associatedvalvular prosthesis is located in the correct area of the patient'sdiseased heart valve.

Among other things, inexact implantation of a sub-optimally positionedvalvular prosthesis can lead to leakage or valvular insufficiency whichresults in considerable ventricular stress. For example, if a valvularprosthesis is implanted too far above the plane of the native heartvalve, this can lead to closure or blocking of the coronary artery ostia(inlet orifice of coronaries) and thus to fatal coronary ischemia andmyocardial infarction.

Therefore, for the optimal treatment of a narrowed cardiac valve or acardiac valve insufficiency, it is necessary to position a stent, towhich a valvular prosthesis is affixed, as precisely as possible at thesite of implantation of the cardiac valve to be treated.

An endoprosthesis for treating aortic valve insufficiency is known fromprinted publication DE 20 2007 005 491 U1. The endoprosthesis comprisesa valvular prosthesis and a stent to position and anchor the valvularprosthesis at the implantation site in the patient's heart. A stenthaving several (multiple, normally three, but two in case of bicuspidvalve) positioning arches is employed in this endoprosthesis. In theimplanted state of the stent, these positioning arches extend radiallyand serve to engage in the pockets of the native (diseased) cardiacvalve to be treated. The valvular prosthesis affixed to the stent canthen self-position into the plane of the cardiac valve. Retaining archesabut against the vascular wall of the aorta in the implanted state ofthe endoprosthesis, form a force-fit connection and are used to anchorthe endoprosthesis.

While the positioning arches enable optimal positioning of the stent ofthis endoprosthesis at the site of implantation in the patient's heart,what cannot be ensured is that the valvular prosthesis attached to theproximal end of the stent is actually also positioned in the plane ofthe cardiac valve. In particular, substantial forces act on the valvularprosthesis during the filling phase of the heart cycle (diastole), whichcan lead to the valvular prosthesis displacing longitudinally relativethe stent. Due to this longitudinal displacement of the implantedvalvular prosthesis, which occurs in the heart and blood vesselsespecially because of the peristaltic motion of the heart, the implantedvalvular prosthesis may no longer be able to provide a secure seal.

Moreover, there is the danger that, because of the longitudinaldisplacement of the valvular prosthesis relative the stent occurringwith the peristaltic motion, the threads or sutures used to fasten thevalvular prosthesis to the stent may chafe against the stent. It cantherefore not be excluded that the fastening threads may fray over thecourse of time and thus lose their fastening function. This would resultin at least a partial separation of the valvular prosthesis from thestent, which in turn can lead to leakages, an inappropriate positioningor even complete detachment of the valvular prosthesis.

On the basis of the problems outlined above, the present inventionaddresses the issue of providing a self-expandable endoprothesis fortreating a narrowed cardiac valve or a cardiac valve insufficiency whichrealizes optimum positioning accuracy and anchoring of a valvularprosthesis to be implanted. In addition, the treatment of the narrowedcardiac valve or cardiac valve insufficiency should be by way of asimple procedure to enable routine treatment of narrowed cardiac valveor cardiac valve insufficiency without major stress to the patient.

A further task of the present invention lies in specifying anendoprothesis for the treatment of a stenosed cardiac valve or a cardiacvalve insufficiency, whereby the endoprothesis can be anchored securelyat the site of implantation in the patent's heart. In addition, thepresent invention also addresses the issue of substantially preventingdisplacement of an implanted valvular prosthesis from its ideal site ofimplantation in spite of the forces acting on the endoprothesis duringthe filling phase of the heart cycle.

From one aspect, an expandable stent is proposed in accordance with thepresent invention, the stent comprising at least one fastening portionby means of which a valvular prosthesis is connected to the stent. Inparticular, the stent comprises both positioning arches and retainingarches. At least one positioning arch of the stent is connected with atleast one retaining arch of the stent by a first connecting web.

Additionally, the stent further comprises at least one auxiliary archwhich interconnects the arms of respective retaining arches.

The at least one fastening portion extends along the longitudinal axisof the stent and comprises a plurality of fastening holes distributed ina longitudinal direction at discrete positions along the length of theat least one fastening portion. Thread or thin wire may be guidedthrough each fastening hole to secure the valvular prosthesis to thestent. The advantage of this feature is that longitudinal displacementof the valvular prosthesis relative to the stent is substantiallyminimized once implanted and so the prosthesis is not unduly disturbedor weakened as a result of the heart's peristaltic motion.

Depending from and between a pair of fastening portions is a fasteningarch, over which valve tissue is laid. The fastening arch is locatedinside the circumference of the stent. In this way, the prosthesistissue is separated and held away from positioning and retaining arches,thereby reducing the likelihood of these arches chaffing the tissuewhich, in turn may result in damage and weakening of the prosthesis. Thefastening arch serves to anchor the lower edge of the valvularprosthesis and to tension the material so the prosthesis is effective asa valve. By having a fastening portion and fastening arches, theprosthesis is fully supported and anchored within the boundary of thestent. The combination of the two fastening mechanisms also provides afailsafe should one fastening mechanism fail. This is of particularrelevance with suturing since a poorly sutured prosthesis will not be aseffective as it should due to additional stresses and strains impartedto the prosthesis by the sutures. Thus, the arches allow fastening ofthe prosthesis in a manner that does not rely solely on suturing.

In an implanted configuration, the at least one positioning arches ofthe stent extends from the circumference of the stent in a generallyradial direction. These positioning arches are designed to engage in thepockets of the native (diseased) cardiac valve that is being replacedwhich, in turn allows accurate positioning of the stent. Furthermore, onimplantation, a positioning arch sits between the vascular wall and aleaflet of the native heart valve. The positioning arch then co-operateswith a corresponding retaining arch resulting in clipping of the nativeleaflet between the two arches. In this way, the positioning andretaining arches together hold the stent in position and substantiallyeliminate axial rotation of the stent.

The at least one retaining arch is connected to a positioning arch by aconnecting web. The retaining arch extends radially in the implantedstate of the stent such that the at least one retaining arch pressesagainst the wall of the blood vessel in which the stent is deployed witha radially-acting tensioning force. In addition to the at least oneretaining arch, the invention provides for the stent to further compriseat least one auxiliary arch which interconnects the respective arms ofthe at least one retaining arch connected to the at least onepositioning arch. As with the at least one retaining arch, the at leastone auxiliary arch also protrudes radially in the expanded state of thestent when implanted such that the at least one auxiliary arch alsopresses against the wall of the blood vessel in which the stent isdeployed with a radially-acting tensioning force.

In the at least one fastening portion of the stent, by means of whichthe valvular prosthesis can be fastened to the stent, a plurality offastening holes is provided. These fastening holes are longitudinallydistributed at given positions on the fastening portion and guide atleast one thread or thin wire to fasten the valvular prosthesis to thestent, thereby enabling a precise positioning of the valvular prosthesison the stent. Each individual fastening hole provided in the at leastone fastening portion thereby serves to guide a thread or thin wire withwhich the valvular prosthesis is affixed or sewn to the fasteningportion of the stent.

The means provided for fastening the valvular prosthesis to thefastening portion of the stent (thread or thin wire) is guided by way ofthe fastening holes so that a longitudinal displacement of the valvularprosthesis relative the stent is substantially minimized. This alsoallows exact positioning of the valvular prosthesis relative the stent.

The secure and defined fixing of the valvular prosthesis to the at leastone fastening portion of the stent moreover effectively prevents themeans used to fasten the valvular prosthesis to the stent (threads orthin wires) from rubbing against the stent and thus degrading after alonger period of use.

In order to configure the plurality of fastening holes in the fasteningportion, the at least one fastening portion is preferably configuredas—in comparison to the respective arms of the positioning arch,retaining arch and auxiliary retaining arch—a widened segment. Thus, thefastening portion is a stent segment which comprises a relatively largeamount of material, facilitating movement and position analysis when thestent is being implanted. For example, when fluoroscopy (cardiaccatheterization=LHK) or ultrasound (trans-esophageal echocardiogram=TEE)is used to monitor the insertion procedure, the fastening portion of thestent is particularly distinguishable.

In manufacturing the stent used in the endoprothesis according to theinvention, it is conceivable for the stent to exhibit a structureintegrally cut from a portion of tube, in particular from a small metaltube, which incorporates the positioning arches, retaining arches andauxiliary retaining arches as well as the at least one fastening portionwith the defined fastening holes. Specifically, it is conceivable to usea laser to cut the stent structure from the small metal tube, wherebythe structure is thereafter subject to an applicable shaping and thermaltreatment process so that the stent can transform from a collapsed stateduring implantation into an expanded state at the site of implantation.This shaping and thermal treatment process is advantageously performedgradually in order to prevent damage to the stent structure.

Particularly preferred is for the stent to exhibit a structureintegrally cut from a small metal tube in which each positioning arch isallocated one retaining arch, and in which each upper end portion of thepositioning arch towards the upper end of the stent is connected withthe upper end portion of the associated retaining arch via a firstconnecting web. The at least one fastening portion, in which theplurality of fastening holes is provided, is thereby preferablyconfigured within an arm of the retaining arch.

It is to be understood that the term “upper” refers to the stent whenviewed in its implanted state. In other words, the term “upper” refersto the distal end of the stent which, when implanted, is sited away fromthe heart. Similarly, use of the term “lower” refers to a proximalposition on the stent which is located towards the heart when the stentis viewed in its implanted position.

A preferred realization of the stent according to invention provides fora fastening portion to be configured within each arm of the stent'sretaining arch.

In order to be able to reinforce the respective retaining arches of thestent, the auxiliary arch as already mentioned above is provided andwhich extends from the lower ends of the fastening portion and connectsthe respective arms of two neighboring retaining arches.

The stent preferably exhibits an integrally-formed structure which cantransform from a first predefinable shape into a second predefinableshape, whereby the stent exhibits a first predefinable shape (collapsedshape) during insertion into the patient's body and a secondpredefinable shape (expanded shape) once implanted. Because of thestent's design, during the transition of the stent from the firstpredefinable shape into the second predefinable shape, the positioningarches, retaining arches and auxiliary arches are radially expanded as afunction of the cross-sectional expansion of the stent. The stent'ssecond shape is thereby preferably selected such that when expanding,the retaining arch and the auxiliary arch abut against the wall of theblood vessel in which the stent is deployed.

To achieve a secure anchoring of the stent at the site of implantation,both the retaining and auxiliary arches should press against the wall ofthe vessel with a radial force, whereby this radial force can be set bysubjecting the stent structure to a suitable shaping and thermaltreatment process.

A preferred embodiment of the stent according to the invention providesfor the positioning arches and the associated retaining arches as wellas auxiliary arches each to exhibit an essentially U-shaped, T-shaped orV-shaped structure which is closed toward the lower end of the stent. Itis particularly preferred for each positioning arch to be cut from thematerial portion of a small metal tube from which the essentiallyU-shaped, T-shaped or V-shaped structure of the associated retainingarch was taken. The respective auxiliary arches are preferably cut froma material portion of the small metal tube situated between theessentially U-shaped, T-shaped or V-shaped retaining arch structures.

This preferred embodiment of the stent structure thus provides for therespective retaining and auxiliary arches of the stent to form the lowerregion of the endoprothesis, whereby the positioning arches areconfigured symmetrically to the retaining arches although preferablydisposed somewhat farther toward the upper region of the endoprothesis.

The respective upper ends of the positioning arches are connected to therespective upper ends of the associated retaining arches by means of afirst connecting web in the upper region of the endoprothesis. Thefastening portions are configured in the respective arms of theretaining arch. In the expanded state of the stent, both the lowerregion with the fastening portions, as well as the connecting webdisposed at the upper end of the stent between the respectivepositioning and retaining arches, spread out so that a radially-actingforce is exerted on the blood vessel wall from both the lower region ofthe stent as well as the upper end of the stent, thereby enabling secureanchoring of the stent at the site of implantation.

In a preferred embodiment, the stent exhibits in its first shape(collapsed shape) an outer diameter of approximately 4 to 8 mm and alength of between 30 mm and 40 mm, preferably between 34.0 and 39.0 mm,and more preferably between 34.37 mm and 38.37 mm. This allows the stentto be inserted easily into the patient's body, for example with a 21Fdelivery system, and to be used with a valvular prosthesis having adiameter of between 19 mm and 28 mm. The afore-mentioned lengthspecifications are the dimensions currently preferred, based on whichthe stent becomes suitable for the majority of patients to be treated.

In order to achieve a particularly secure anchoring of the implantedstent with the stretched valvular prosthesis affixed thereto, it isfurther conceivable for the stent to be subject to a shaping and thermaltreatment process during its manufacture such that the finished stentexhibits a slightly concave configuration tapering toward its lower endin its second shape.

In other words, the lower end portion of the stent; i.e., that area inwhich the valvular prosthesis is fastened, exhibits a somewhat tapereddiameter in comparison to the upper end portion. Specifically, it hasbeen seen that, when the stent is in it second shape and the upper endof the stent exhibits a diameter approximately 10-25% larger than thediameter of its lower end, radial forces are generated particularly atthe stent's upper end. This enables a secure hold of the stent in theblood vessel without damaging the arterial wall. This configuration alsoprovides secure anchoring that is able to withstand the peristalticmotion of the heart and the arterial wall. The somewhat lesser radialforce exerted by the lower end of the stent not only serves to anchorthe stent in the blood vessel but also to stretch the valvularprosthesis attached at the lower end and reliably seal the prosthesisagainst the arterial wall. It is of course also conceivable to designthe concave configuration of the stent in its second shape to be ofgreater or lesser concavity.

It is preferable for the lower end area of the stent, when in its secondshape, to exhibit a diameter of between 22 mm and 33 mm, preferablybetween 25 mm and 31 mm. It is conceivable for the stent to exhibit twoor more differently dimensioned sizes whereby the optimal stent size canbe selected depending upon specific patient. In addition, exact andpatient-specific dimensions of the stent—starting from a given stentsize—can be realized by appropriately curing the stent, in particular bya thermal treatment process.

In a particularly preferred realization, the stent comprises a valvularprosthesis, preferably a biological valvular prosthesis, which isattached to the at least one fastening portion of the stent by means ofa thread or the like.

A shape memory material is preferably used as the material for thestent, the material being designed such that the stent can transformfrom a temporary shape into a permanent shape under the influence of anexternal stimulus. The temporary shape is thereby the stent's firstshape (i.e. the collapsed state of the stent), while the permanent shapeis assumed in the stent's second shape (i.e. in the expanded state ofthe stent). In particular, use of a shape memory material such asnitinol, i.e. an equiatomic alloy of nickel and titanium, allows for aparticularly gentle implantation procedure when implanting the stent.

When manufacturing the stent preferably made from a shape memorymaterial, the stent structure is preferably shaped after it has been cutfrom a tube. Once the desired shape has been formed, this shape is“fixed”, this process being known as “programming.” Programming may beeffected by heating the scent structure, forming the stent into thedesired shape and then cooling the stent. Programming may also beeffected by forming and shaping the stent structure at lowertemperature, this being known as “cold stretching.” The permanent shapeis thus saved, enabling the stent to be stored and implanted in atemporary, non-formed shape. If an external stimulus then acts on thestent structure, the shape memory effect is activated and the saved,permanent shape restored.

A particularly preferred embodiment provides for the external stimulusto be a definable switching temperature. It is thus conceivable that thestent material needs to be heated to a higher temperature than theswitching temperature in order to activate the shape memory effect andthus regenerate the saved permanent shape of the stent. A specificswitching temperature can be preset by the relevant selection of thechemical composition of the shape memory material.

It is particularly preferred to set the switching temperature to be inthe range between room temperature and the patient's body temperature.Doing so is of advantage, especially with regard to the medical devicebeing used as an implant in a patient's body. Accordingly, all thatneeds to be ensured in this regard when implanting the stent is that thestent is warmed up to the patient's body temperature (36° C.) at thesite of implantation to activate the shape memory effect of the stentmaterial.

The following will make reference to the included drawings in describingpreferred embodiments of the stent according to the present invention ingreater detail.

Shown are:

FIG. 1 a a perspective side view of a cardiac valve stent in accordancewith a first embodiment of the invention, where the cardiac valve stentis shown in its collapsed state;

FIG. 1 b a perspective side view of the cardiac valve stent inaccordance with the first embodiment of the invention, where the cardiacvalve stent is shown in its expanded state;

FIG. 1 c a perspective top plan view of the proximal end of the cardiacvalve stent in accordance with the first embodiment of the invention,where the cardiac valve stent is shown in its expanded state;

FIG. 1 d a perspective side view of an endoprothesis for treating anarrowed cardiac valve or a cardiac valve insufficiency, where theendoprothesis comprises the cardiac valve stent according to the firstembodiment of the invention for holding a valvular prosthesis;

FIG. 1 e a two-dimensional projection of a cutting pattern applicable tomanufacturing the cardiac valve stent according to the first embodimentof the invention in order to cut a cardiac valve stent pursuant FIG. 1 aintegrally from a portion of tube, in particular a small metal tube;

FIG. 2 a a perspective side view of a cardiac valve stent according to asecond embodiment of the invention, where the cardiac valve stent isshown in its collapsed state;

FIG. 2 b a first perspective side view of the cardiac valve stentaccording to the second embodiment of the invention, whereby the cardiacvalve stent is shown in its expanded state;

FIG. 2 c a second perspective side view of the cardiac valve stentaccording to the second embodiment of the invention, where the cardiacvalve stent is shown in its expanded state;

FIG. 2 d a perspective side view of an endoprothesis for treating anarrowed cardiac valve or a cardiac valve insufficiency, where theendoprothesis comprises the cardiac valve stent according to the secondembodiment of the invention for holding a valvular prosthesis;

FIG. 2 e a two-dimensional projection of a cutting pattern applicable tomanufacturing the cardiac valve stent according to the second embodimentof the invention in order to cut a cardiac valve stent pursuant FIG. 2 aintegrally from a portion of tube, in particular a small metal tube; and

FIG. 3 a-c a process sequence illustrating a transarterial implantationof an endoprothesis comprising a cardiac valve stent in accordance withthe invention.

Both the right and left halves of the human heart consist of a ventricleand an atrium. These cavities are separated by the septum of the heart,divided into the atrial septum (septu interatriale) and the ventricularseptum (septr itervntricalare).

Blood can only flow in one direction through the chambers of the heartdue to the cardiac valves situated between the atria and ventricles andin the arteries connected to the ventricles which function likemechanical valves. The superior and inferior vena cava (sena canasperior et inferior) flow into the right atrium. They supply theoxygen-depleted (venous) blood from the systemic circulation to theheart. The tricuspid valve which, like a mechanical valve, prevents areverse flow of blood into the atrium upon ventricular contraction(systole) is situated between the right atrium and the right ventricle.It comprises three segments which are affixed like flaps to theventricular musculature by ligaments (hence also called the “flapvalve”). The two pulmonary arteries depart the right ventricle of theheart via a common trunk (trncwsp/mona/is). There is also a valvebetween the ventricle and the pulmonary trunk, the so-called pulmonaryvalve. This type of valve is also called a semilunar valve due to itsshape. The pulmonary arteries supply the oxygen-depleted blood to thepulmonary circulation.

Oxygen-rich (arterial) blood then usually flows through four pulmonaryveins from the pulmonary circulation to the left atrium. From there, itreaches the left ventricle through a further flap valve, the mitralvalve. The outflow is carried by the aorta which, like the pulmonaryartery, has a semilunar valve (aortic valve).

During a heart cycle, the atria fill first while the ventriclesconcurrently disgorge the blood into the arteries. When the ventricularmusculature relaxes, the flap valves open due to the drop in pressure inthe ventricle and the blood flows in from the atria (auricular systole).This is supported by a contraction of the atria. Ventricular contractionfollows: the ventricular musculature contracts, the pressure rises, theflap valves close and the blood can now only flow into the arteriesthrough the now-opened semilunar valves.

A reverse blood flow from the arteries during the relaxation phase(diastole) is prevented by the closing of the semilunar valves such thatthe direction of flow is determined solely by the valves.

The four cardiac valves work like mechanical valves in the heart andprevent a reverse flow of blood in the wrong direction. Each half of theheart has a flap valve (atrioventricular valve) and a semilunar valve.The atrioventricular valves are situated between the atrium and theventricle and are called the bicuspid/mitral valve and the tricuspidvalve. The semilunar valves are situated between the ventricle and thevascular outflow and are called the pulmonary valve and the aortic valverespectively.

A valve defect; i.e. a dysfunctioning of a cardiac valve's function, canaffect any of the four cardiac valves, although the valves on the leftside of the heart (aortic and mitral valves) are affected considerablymore frequently than those on the right side of the heart (pulmonary andtricuspid valves). Dysfunction can encompass constriction (stenosis),insufficiency or a combination of the two (combined vitium).

In medicine, the term “aortic valve insufficiency”, or “aorticinsufficiency” for short, refers to the defective closing of the heart'saortic valve and the diastolic reverse flow of blood from the aorta intothe left ventricle as a result. Depending on the severity of the aorticinsufficiency and the extent of resistance to aortic depletion, thevolume of reverse flow can be up to two thirds of the left ventricle'sejection volume (normal cardiac output 40 to 70 ml). This results incharacteristically high blood pressure amplitude. This regurgitantbloodflow increases the diastolic filling of the left chamber and leadsto a volume overload of this section of the heart, a consequence ofwhich is eccentric hypertrophy.

Aortic valve stenosis is a valvular heart disease caused by theincomplete opening of the aortic valve. When the aortic valve becomesstenotic, it causes a pressure gradient between the left ventricle andthe aorta. The more constricted the valve, the higher the gradientbetween the left ventricle and the aorta. For instance, with a mildaortic valve stenosis, the gradient may be 20 mmHg. This means that, atpeak systole, while the left ventricle may generate a pressure of 140mmHg, the pressure that is transmitted to the aorta will only be 120mmHg.

In individuals with Aortic valve stenosis, the left ventricle has togenerate an increased pressure in order to overcome the increasedafterload caused by the stenotic aortic valve and eject blood out of theleft ventricle. The more severe the aortic stenosis, the higher thegradient is between the left ventricular systolic pressures and theaortic systolic pressures. Due to the increased pressures generated bythe left ventricle, the myocardium (muscle) of the left ventricleundergoes hypertrophy (increase in muscle mass).

Angina in the setting of aortic valve stenosis is secondary to the leftventricular hypertrophy that is caused by the constant production ofincreased pressure required to overcome the pressure gradient caused bythe aortic valve stenosis. While the myocardium (i.e. heart muscle) ofthe left ventricle gets thicker, the arteries that supply the muscle donot get significantly longer or bigger, so the muscle may becomeischemic (i.e. doesn't receive an adequate blood supply). The ischemiamay first be evident during exercise, when the heart muscle requiresincreased blood supply to compensate for the increased workload. Theindividual may complain of exertional angina. At this stage, a stresstest with imaging may be suggestive of ischemia.

Mitral valve insufficiency (also called mitral insufficiency) is afrequent cardiac valve defect in human medicine and also in at leastsome animal species. It involves a closing defect or “leakage” of theheart's mitral valve which leads to reverse bloodflow from the leftventricle into the left atrium during the ejection phase (systole).

The mittal valve functions like a mechanical valve between the leftatrium and the left ventricle of the heart. It opens during the fillingphase of the ventricle (diastole) and thus enables the inflow of bloodfrom the atrium. At the beginning of the ejection phase (systole), thesudden increase in pressure in the ventricle leads to the closing of thevalve and thus to a “sealing” of the atrium. In so doing, a pressure ofonly about 8 mmHg prevails in the atrium, while at the same time thesystolic pressure of about 120 mmHg in the ventricle forces the bloodalong its usual path into the main artery (aorta).

In cases of severe mitral insufficiency, however, the regurgitationopening is larger than 40 mm² and the regurgitation volume greater than60 ml, which can lead to serious and at times life-threatening changes.

In the acute stage, with a normal size to the left ventricle and theleft atrium, there is a considerable increase of the pressure in theatrium and thus also in the pulmonary veins. This can be up to 100 mmHgwhich, given a normal condition to the pulmonary vessels, leads toimmediate pulmonary edema. The then predominantly reverse blood flow canmoreover result in insufficient ejection outflow into the aorta and thusdecreased blood flow to all the organs.

To treat a severe narrowed cardiac valve or cardiac valve insufficiency,it is necessary for a valvular prosthesis to perform the valve functionof the narrowed, diseased or diseased cardiac valve. Essential in thisrespect is that the valvular prosthesis is securely positioned andanchored in the implantation site in the heart; i.e. in the plane of the(diseased) cardiac valve to be replaced, so that the valvular prosthesisis not displaced or shifted despite the, at times considerable, forcesacting on it. An effective seal during systole is also important.

A cardiac valve stent 10, to which the valvular prosthesis 100 isappropriately affixed, is employed in accordance with the invention toposition and anchor said valvular prosthesis. A medical device for thetreating of a narrowed cardiac valve or a cardiac valve insufficiencyconsisting of a cardiac valve stent 10 and a valvular prosthesis 100affixed to the stent 10 will be referred to herein simply asendoprothesis 1.

FIG. 1 d shows a perspective side view of such an endoprothesis 1 fortreating a narrowed cardiac valve or a cardiac valve insufficiency,whereby the endoprothesis 1 comprises a cardiac valve scent 10 to hold avalvular prosthesis 100 in accordance with a first embodiment of theinvention. FIG. 2 d likewise shows a perspective side view of a furtherendoprothesis 1 for treating a narrowed cardiac valve or a cardiac valveinsufficiency, whereby here a cardiac valve stent 10 in accordance witha second embodiment of the invention is employed.

The following will make reference to the included drawings in describingthe presently preferred embodiments of the present invention in detail.The cardiac valve stent 10 according to the invention (hereinafterreferred to simply as “stent”) exhibits an expandable structure which isable to transform from a first predefinable shape in which the stent 10is in a collapsed state into a second predefinable shape in which thestent 10 is in an expanded state. FIG. 1 a shows a perspective side viewof the stent 10 according to the first embodiment of the invention,whereby the stent 10 is in its collapsed state. FIG. 2 a shows thecollapsed stent 10 according to the second embodiment of the invention.

In the two embodiments, the scent 10 can be introduced inminimally-invasive fashion into the body of a patient in its first shape(cf. FIG. 1 a and FIG. 2 a) using an insertion catheter system (notexplicitly shown in the drawings). During insertion, the valvularprosthesis 100 affixed to the stent 10 is likewise in a collapsed state.For the sake of clarity, however, both FIGS. 1 a and 2 a dispense with arepresentation of the valvular prosthesis 100 affixed to the stent 10.

Upon reaching the site of implantation in the patient's heart, the stent10 transforms, preferably incrementally, into its second (expanded)shape in which also the valvular prosthesis 100 affixed to the stent 10unfolds and expands. The second, expanded shape is a permanent shapethat has been set by programming. The completely expanded stent 10according to the first/second embodiment of the invention with thelikewise completely unfolded and expanded valvular prosthesis 100affixed thereto is shown in FIG. 1 d and FIG. 2 d.

FIG. 1 b and FIG. 1 c show the completely expanded stent 10 according tothe first embodiment of the invention without the valvular prosthesis100 from respectively different perspectives. FIGS. 2 b and 2 c show thecompletely expanded stent 10 according to the second embodiment of theinvention, likewise without the valvular prosthesis 100, fromrespectively different perspectives.

The following will initially make reference to FIGS. 1 a to 1 e indescribing the first embodiment of the inventive cardiac valve stent 10.

The stent 10 according to the first embodiment exhibits a structureintegrally cut from a portion of tube, in particular a small metal tube.The cutting pattern used to form the design of the stent is depicted ina two-dimensional projection in FIG. 1 c.

In detail, the stent 10 of the depicted first embodiment comprises atotal of three positioning arches 15 a, 15 b, 15 c which assume thefunction of self-positioning the stent into the plane of the pulmonaryvalve (mala trunci pulmonalis) or aortic valve (valva aortae). Thepositioning arches 15 a, 15 b, 15 c exhibit a rounded head portion 20which engages in the pockets T of the (diseased) cardiac valve to betreated during positioning of the stent 10 at the site of implantationin the heart (cf. FIG. 3 a).

Providing a total of three positioning arches 15 a, 15 b, 15 c allowsfor the required positioning accuracy of stent 10 in the direction ofrotation. The invention is of course not limited to the use of a totalof three positioning arches.

The head portions 20 of the positioning arches 15 a, 15 b, 15 c,respectively pointing towards the lower end 2 of the stent 10, arecorrespondingly rounded so that the vascular wall will not be damagedwhen the positioning arches 15 a, 15 b, 15 c engage in the pockets T ofthe cardiac valve H to be replaced. It is moreover preferred withrespect to improving movement and position analysis during theimplanting of the stent 10 for reference markers 21 to be provided on orwithin the head portions 20 of the positioning arches 15 a, 15 b, 15 c.Radio opaque markers or markers which can be activated by infrared orultrasound lend themselves particularly well hereto.

Specifically, the positioning arches 15 a, 15 b, 15 c respectivelyexhibit an essentially U-shaped or V-shaped structure which is closed tothe lower end of stent 10. Accordingly, each positioning arch 15 a, 15b, 15 c has a total of two arms 15 a′, 15 a″, 15 b′, 15 b″, 15 c′, 15 c″respectively extending from the head portion 20 of the associatedpositioning arch 15 a, 15 b, 15 c toward the upper end 3 of stent 10. Bydoing so, each two adjoining arms of two neighboring positioning archesare connected to one another via a connecting portion 22.

For implanting and explanting the stent 10 with a suitable cathetersystem, the stent 10 comprises catheter retaining means 23 at its upperend 3. The respective connecting portions 22, via which two respectivelyadjoining arms of two neighboring positioning arches are connectedtogether, are respectively connected to catheter retaining means 23 viaa connecting web 25. The connecting webs 25, which connect theconnecting portions 22 to the associated catheter retaining means 23,will herein be referred to as “second connecting web 25.”

In the stent 10 according to the first embodiment of the invention, thecatheter retaining means 23 comprise oval-shaped heads which eachrespectively comprise a likewise oval-shaped eyelet 24. Conceivablehereto would be providing a crown with a total of three protrudingelements in the tip of a catheter of a catheter system used toimplant/explant stent 10. The protruding elements of the crown arethereby to be configured complementary to the eyelets 24 which aredisposed on the catheter retaining means 23 provided at the upper end 3of stent 10 and configured as catheter retaining heads. This realizationwould enable the protruding elements of the crown to form a releasableengagement with the upper area 3 of stent 10 to releasably attach stent10 to the tip of the catheter of the catheter system used toimplant/explant stent 10.

The upper end portion 17 d of a first connecting web 17 extendingessentially in longitudinal direction L of stent 10 furthermore opens toeach connecting portion 22 between the two arms 15 a′, 15 a″, 15 b′, 15b″, 15 c′, 15 c″ of two neighboring positioning arches 15 a, 15 b, 15 cin addition to the previously-mentioned second connecting web 25. As canbe seen in FIG. 1 b, the respective first connecting webs 17 are ofessentially Y-shaped configuration and each exhibit a structure that isspread at its lower end 17 p which gives way to the respective arms 16a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of two neighboring retainingarches 16 a, 16 b, 16 c.

This stent design achieves an axially symmetrical structure, wherebyeach positioning arch 15 a, 15 b, 15 c is allocated one retaining arch16 a, 16 b, 16 c. The stent 10 of the first embodiment depicted in FIGS.1 a to 1 d thus comprises a total of three retaining arches 16 a, 16 b,16 c which constitutes a retaining segment of stent 10 for accommodatinga valvular prosthesis 100 as depicted for example in FIG. 1 d.

In the state of the stent 10 shown in FIG. 1 a, in which stent 10 is inits first (collapsed) shape, the respective arms 15 a′, 15 a″, 15 b′, 15b″, 15 c′, 15 c″ of the positioning arches 15 a, 15 b, 15 c directlyadjoin the respective arms 16 a′, 16 a″, 16 b′, 16 b″, 16 c′, 16 c″ ofthe associated retaining arches 16 a, 16 b, 16 c.

Reference is made to FIG. 1 b, in which the stent 10 pursuant the firstembodiment is shown in its second shape. It can be particularlyrecognized from this representation that each positioning arch 15 a, 15b, 15 c and associated retaining arch 16 a, 16 b, 16 c respectivelyexhibit an essentially U-shaped or V-shaped structure which is closedtowards the lower end 2 of the stent 10. Specifically, each positioningarch 15 a, 15 b, 15 c is cut from a material section of a portion of atube from which the essentially U-shaped or V-shaped structure of theassociated retaining arch 16 a, 16 b, 16 c was taken, as can be seenfrom the cutting pattern depicted in FIG. 1 e.

A comparison of FIG. 1 a to FIG. 1 b shows that, upon the stent 10expanding; i.e. when the stent 10 transforms from its first shape intoits second shape, the stent 10 shortens in the longitudinal direction Lwhile simultaneously enlarging in cross-section. In the expanded stateof stent 10, the respective positioning arches 15 a, 15 b, 15 c areexpanded more in the radial direction at the lower end 2 of the stent 10compared to the upper end 3 of stent 10. Since they protrude more in theradial direction, the positioning arches 15 a, 15 b, 15 c can bedeployed into the cardiac valve pockets T of the cardiac valve H to bereplaced in particularly easy manner.

Even when a certain anchoring of the stent 10 is achieved at the site ofimplantation in the heart due to the positioning arches 15 a, 15 b, 15 calready protruding radially from stent 10 in the expanded state of thestent 10, it is noted that the contact force acting on the vascular wallfrom the positioning arches 15 a, 15 b, 15 c is insufficient to securelyanchor the stent 10 at the site of implantation. Thepreviously-mentioned retaining arches 16 a, 16 b, 16 c, which form thelower end 2 of stent 10, are provided for this reason. The retainingarches 16 a, 16 b, 16 c protrude radially from the circumference of thestent 10 in its expanded state such that the retaining arches 16 a, 16b, 16 c press against the wall of the blood vessel in which the stent isdeployed with a radially-acting contact force.

In addition to retaining arches 16 a, 16 b, 16 c, the stent 10 furthercomprises auxiliary arches 18 a, 18 b, 18 c, which likewise exert aradially-acting contact force against the wall of the blood vessel inthe implanted state of stent 10, thereby improving anchoring of stent 10at the site of implantation.

As can be seen from FIG. 1 b, stent 10 pursuant the first embodimentcomprises a total of three essentially U-shaped or V-shaped auxiliaryarches 18 a, 18 b, 18 c which are closed towards the lower end 2 of saidscent 10. Each auxiliary arch 18 a, 18 b, 18 c connects a firstretaining arch 16 a, 16 b, 16 c with a second retaining arch neighboringthe first retaining arch.

In a top plan view of the lower end region 2 of the expanded stent 10(cf. FIG. 1 c), the lower end region 2 exhibits a dodecagonal polygonalstructure formed from the individual arms 16 a′, 16 a″, 16 b′, 16 b″, 16c′, 16 c″ of retaining arches 16 a, 16 b, 16 c and the individual arms18 a′, 18 a″, 18 b′, 18 b″, 18 c′, 18 c″ of the auxiliary arches 18 a,18 b, 18 c. This stent design particularly provides a total of sixarches 16 a, 16 b, 16 c, 18 a, 18 b, 18 c uniformly distributed aroundthe lower end region 2 of stent 10, each of which press against thevascular wall and effectively hold the stent 10 in position in theexpanded and implanted state of stent 10.

To recapitulate, providing retaining arches 16 a, 16 b, 16 c on the onehand and auxiliary arches 18 a, 18 b, 18 c on the other results in aradial force being exerted on the vascular wall by the respective lowerend portions of these arches. This ensures both a secure seal of avalvular prosthesis 100 affixed to stent 10 relative the vascular wall,as well as a secure anchoring of the stent 10, at the site ofimplantation in the heart.

In addition to the contact force exerted on the vascular wall by way ofthe retaining arches 16 a, 16 b, 16 c and auxiliary arches 18 a, 18 b,18 c, it is conceivable for the upper end region 3 of stent 10 to expandradially 10-25% more—in the expanded state of stent 10—compared to thelower end region 2. This gives the stent 10 a slight concave structurewhich tapers towards the lower end region 2. This ensures secureanchoring of the stent 10 within the vessel by the upper end region 2 ofthe scent 10 pressing against the vascular wall.

Furthermore, to ensure that minimal longitudinal displacement of avalvular prosthesis affixed to stent 10 can occur relative stent 10,even during the peristaltic movement of the heart and the blood vesselin which stent 10 is deployed, the embodiment of the inventive stent 10depicted in the drawings provides for the stent 10 to comprise aplurality of fastening portions 11 a to 11 f extending in thelongitudinal direction L of stent 10, by means of which a valvularprosthesis 100 is affixed to the stent 10. Reference is made to FIG. 1 dwhich shows a perspective side view of an endoprothesis 1 for treating anarrowed cardiac valve or a cardiac valve insufficiency, whereby theendoprothesis 1 comprises the stent 10 pursuant the first embodiment ofthe invention for holding a valvular prosthesis 100. The valvularprosthesis 100 comprises at least one valve flap 102 made from abiological or synthetic material.

It will be appreciated that the valvular prosthesis may be made from anysuitable material, including biological valves removed from animals suchas pigs and horses, man-made biological valves created from connectivetissue such as pericardium, tissue grown from cell cultures, andman-made materials and fabrics such as nitinol.

In detail, the first connecting webs 17 of stent 10 connect withconnecting portions 22 via their upper ends 17 d and with the upper ends13 of fastening portions 11 via their lower ends 17 p. The respectivelower ends 14 of the fastening portions which are connected to one andthe same connecting web 17 are thereby connected together via anessentially U-shaped or V-shaped auxiliary arch 18 a, 18 b, 18 c whichis closed towards the lower end 2 of stent 10.

Specifically, the first embodiment of the inventive stent 10 is shown inFIG. 1 d in its expanded state, whereby a valvular prosthesis 100 isfastened to said stent 10 by means of a thread 101 or a thin wire andstretched by the stent 10. It is easily recognized that the widening ofthe center area and the lower end region 2 of stent 10 at which thevalvular prosthesis 100 is disposed achieves spreading of the valvularprosthesis. At the same time, the lower end portions of the retainingarches 16 a, 16 b, 16 c and the auxiliary arches 18 a, 18 b, 18 c exerta radial force on the (not shown in FIG. 1 d) vascular wall.

As can be seen from FIG. 1 d, a defined plurality of fastening holes 12are configured in the respective fastening portions 11 a to 11 f ofstent 10, the same being arranged to be distributed at predefinedlongitudinal positions along the fastening portions 11 a to 11 f. Thethread 101 or thin wire with which the valvular prosthesis 100 isattached to stent 10 is guided through each respective fastening hole12.

Both components constituting the endoprothesis 1, namely the stent 10and the valvular prosthesis 100, are preferably not connected togetheruntil directly prior to the surgical procedure. This is of advantage interms of transport and storage since the stent 10 is a relatively sturdycomponent mechanically and can be stored for a long period of timewithout degradation. This is particularly true when the stent 10 isstored in its second shape; i.e. in the expanded state, and not broughtinto its first (collapsed) shape until directly prior the surgicalprocedure.

It can be noted from FIGS. 1 b and 1 d that the respective fasteningportions 11 a to 11 f are configured in the respective arms 16 a′, 16a″, 16 b′, 16 b″, 16 c′, 16 c″ of retaining arches 16 a, 16 b, 16 c ofstent 10. The size of the fastening holes 12 configured in the fasteningportions 11 a to 11 f should be adapted to the thickness of the thread101 or wire used to fasten the valvular prosthesis 100 to the stent 10.

The cross-sectional shape to the fastening holes 12 may also be adaptedto the cross-sectional shape of the thread 101 or wire used to fastenthe valvular prosthesis 100. This allows fixing of the valvularprosthesis 100 to the stent 10 at a precise predefined position relativethe stent 10. By providing of a plurality of fastening holes 12 toanchor the valvular prosthesis 100 to the stent 10, precise positioningof the valvular prosthesis on stent 10 is achieved.

Because the fastening holes 12 are adapted to the thickness and/or thecross-sectional shape of the thread 101 or wire used to affix thevalvular prosthesis 100 to the stent 10, relative movement between thestent 10 and the valvular prosthesis 100 due to the peristaltic motionof the heart can be effectively prevented when the endoprothesis 1 isimplanted. The valvular prosthesis 100 is thus fastened to the stent 10with minimal play, based on which friction-induced wear of the thread101 or wire used to affix the valvular prosthesis is minimized. As shownin the figures the fastening holes 12 have a circular cross-sectionalshape.

As already mentioned, the fastening holes 12 configured in therespective fastening portions 11 a to 11 f may be of differentdiameters, numbers or cross-sectional shapes (oval, square, etc)according to the diameter of a thread 101 used for affixing the valvularprosthesis 100 to the stent 10, and/or according to the sewing techniqueutilized for affixing the valvular prosthesis 100 to the stent 10. Thediameter, number and/or cross-sectional shape of at least one of thefastening holes 12 may also serve as an indication of the type of theendoprosthesis 1, i.e. the medical device used in the treatment of anarrowing of a cardiac valve and/or a cardiac valve insufficiency. Inthis respect, the diameter, number and/or cross-sectional shape of theat least one fastening hole 12 may be used for identification todifferentiate between different sizes or types of valvular prostheses100 adapted to be fixed on the stent 10, or may be used foridentification to differentiate between different sizes or types ofendoprostheses 1, if a valvular prosthesis 100 is already fixed to thestent 10. For example, a small-sized stent 10 having a small-sizedvalvular prosthesis 100 fixed thereto or a small-sized stent 10 adaptedand configured for carrying a small-sized valvular prosthesis 100 couldhave circular fastening holes 12 whilst a large-sized stent 10 having alarge-sized valvular prosthesis 100 fixed thereto or a large-sized stent10 adapted and configured for carrying a large-sized valvular prosthesis100 may have triangular fastening holes 12. This allows thesurgeon/cardio staff to easily and visually tell different valve sizes,stent types and/or types of the endoprosthesis apart without the need tomeasure.

The fastening portions 11 a to 11 f of the stent 10 (onto which thevalvular prosthesis 100 is sewn or sewable) do not change their shapewhen the stent 10 is compressed, e.g. when the stent 10 is in its first(collapsed) shape shown in FIG. 1 a. This phenomenon occurs whenstandard tube stents are used. Thus the risk of thread wear is minimal.

The stent 10 in accordance with the second embodiment depicted in FIGS.2 a to 2 c is fundamentally identical in structural and functionalregard to the stent 10 according to the first embodiment depicted inFIGS. 1 a to 1 c. The same also holds true for the cutting patterndepicted in FIG. 2 e which is, in principle, comparable to the cuttingpattern according to FIG. 1 e. A detailed description of the commonfeatures will therefore not be provided.

The only difference to be seen is in the configuration of the catheterretaining means 23 provided at the distal end 3 of stent 10. In contrastto the first embodiment of the inventive stent 10, heads of anessentially round configuration are used as catheter retaining means 23in the second embodiment, in each case provided with essentially ovaleyelets 24.

As already indicated, the stent 1 according to the present inventionpreferably exhibits a structure integrally cut from a portion of tube,and in particular from a small metal tube, in which a retaining arch 16a, 16 b, 16 c is allocated to each positioning arch 5 a, 15 b, 15 c, andwith which each retaining arch 16 a, 16 b, 16 c is connected by means ofan auxiliary arch 18 a, 18 b, 18 c, whereby a fastening portion 11 witha specific number of fastening holes 12 is configured in each arm 16 a′,16 a″, 16 b′, 16 b″, 16 c′, 16 c″ of retaining arch 16 a, 16 b, 16 c.

FIGS. 1 e and 2 e each show a two-dimensional projection of a cuttingpattern which can be used in the manufacture of the stent 10 pursuantthe first or second embodiment of the invention in order to integrallycut a one-piece stent 10 from a portion of tube, in particular a smallmetal tube. It is evident that, on the one hand, the inventive stent 10dispenses with fixed-body joints or other similar connective devicesbetween the individual components of stent 10 (positioning arch,retaining arch, auxiliary arch). On the other hand, a scent 10 isprovided which exhibits, with minimum longitudinal extension, thefunctionality of positionability as provided by the positioning arches15 a, 15 b, 15 c on the one hand and, on the other, the functionality ofthe defined fastening of a valvular prosthesis 100, as provided by thefastening portions 11 configured in the respective arms 16 a′, 16 a″, 16b′, 16 b″, 16 c′, 16 c″ of the retaining arch 16 a, 16 b, 16 c.

In addition to its retaining arches 16 a, 16 b, 16 c, the stent 10further comprises auxiliary arches 18 a, 18 b, 18 c which enable aparticularly secure anchoring of stent 10 in the site of implantation inthe heart.

The stent 10 is preferably made from a shape memory material. The stateof stent 10 shown in FIG. 1 a or FIG. 2 a, in which the stent 10 is inits first shape and thus in its collapsed state, is the so-called“temporary” shape of the stent structure made from a shape memorymaterial. When an external stimulus acts on the stent structureaccording to FIG. 1 a or FIG. 2 a, the shape memory effect is activatedand thus the predefined permanent shape saved during the manufacture ofthe stent 10 as pursuant, for example, FIG. 1 b or FIG. 2 b, isrestored.

Said external stimulus is preferably a specifiable switching temperaturewhereby, to activate the shape memory effect and thus regenerate thesaved permanent shape of the stent 10, the stent material is warmed to ahigher temperature than the switching temperature. By selecting asuitable chemical composition of the material used for stent 10, aspecific switching temperature can be predefined. In the preferredembodiment of the inventive solution, the switching temperature rangesfrom between about 20° C. and the body temperature of the patient.

When implanting the stent 10, it is conceivable for the stent 10 to becooled during the insertion procedure. Once the stent 10 has been guidedto its desired site of implantation, i.e. to the native cardiac valve H(cf. FIG. 3 a), preferably using a suitable insertion catheter system,the cooling can be stopped. The stent 10 is then allowed to warm up tothe patient's body temperature (36° C.) and the shape memory effect ofthe stent material is thus activated. Due to the self-expanding propertyof stent 10 having been triggered, radial forces are generated which acton the individual components of the stent, in particular on thepositioning arches 15 a, 15 b, 15 c, the retaining arches 16 a, 16 b, 16c and the auxiliary arches 18 a, 18 b, 18 c of the stent 10.

The inventive stent 10, as well as the insertion catheter system used toimplant the stent, are preferably configured so that the stent 10 withthe valvular prosthesis 100 affixed thereto can be introducedtransarterially into the body of the patient. In one example, the stent10 is accommodated in the tip of the catheter of the insertion cathetersystem, the catheter tip being introduced into the body via, forexample, puncture of the A. femoris communis (inguinal artery).

Alternatively, the stent 10 according to the invention is also suitedfor transapical implantation, in which—coming from the apex of theheart—the catheter tip of the insertion catheter system is advanced tothe aortic valve through, for example, the left ventricle. With acatheter rip modified accordingly, an analogous implantation of thestent 10 with the valvular prosthesis 100 is thus possible.

Regardless of whether the stent 10 is delivered to the site ofimplantation via a transarterial or transapical approach, the tip of thecatheter of the insertion catheter system is preferably advanced to theimplantation site using angiographic (angiography) and echocardiographic(ultrasound) control. The actual implantation of stent 10 with theattached valvular prosthesis 100 then follows.

FIGS. 3 a to 3 c schematically show the process sequence to illustratetrans-arterial implantation of an endoprothesis 1 comprising a stent 10in accordance with the invention. As shown, the implantation of thestent 10 with the valvular prosthesis 100 attached thereto ensues suchthat the individual components of the stent 10 accommodated in thecatheter tip K are successively released by appropriately manipulatingthe catheter tip K of an insertion catheter system.

The catheter system used to implant the inventive stent 10 is ideallyconfigured such that a liquid cooling agent can be fed through a hollowinterior of the catheter system to catheter tip K. The liquid coolingagent, for example in the form of a saline solution, maintains the stent10 accommodated in the catheter tip K at a temperature below theswitching temperature while the catheter tip K is being advanced to thesite of implantation. This is of particular advantage when a shapememory material is provided as the material of the stent 10. This isbecause the stent 10 transforms from a temporary shape into a permanentshape upon the influence of an external stimulus. The temporary shape isthe first shape of stent 10 (in collapsed state, when the stent 10 isaccommodated in the catheter tip K of the insertion system) and the“permanent shape” is the second shape of stent 10 (the expanded state ofthe stent 10 after the stent 10 has been released from the catheter tipK).

It is to be noted that the “permanent shape” of the expanded stent 10conforms to the native shape of its environment. This allows forvariations in the shape of the environment at the site of implantationwhich will vary from patient to patient. This property of stent 10,related to the “permanent shape” of the expanded stent 10 automaticallyadapting completely to the native shape of its environment, will thusalways ensure that the valvular prosthesis 100 is optimally implanted.

Because a shape memory material such as nitinol, i.e. an equiatomicalloy of nickel and titanium, can be used for the inventive stent 10, aparticularly gentle implantation procedure is achievable when implantingthe stent 10 with the valvular prosthesis 100 affixed thereto.

The stent 10 accommodated in the catheter tip K can be cooled byflushing the insertion catheter system with a suitable cooling agentwhile the catheter tip K is being advanced to keep the temperature ofthe stent material below the critical transition temperature. Once thecatheter tip K with the cooled stent 10 has been advanced to the site ofimplantation, cooling of the stent 10 should be stopped, as aconsequence of which the stent 10 warms up to the body temperature (36°C.) of the patient and the shape memory effect of the stent material isthus activated.

Once the self-expanding property of the individual components of stent10 have been activated, radial forces are generated which act on theindividual components of stent 10, in particular on the positioningarches 15 a, 15 b, 15 c, the retaining arches 16 a, 16 b, 16 c and theauxiliary arches 18 a, 18 b, 18 c of stent 10. Since the respectivecomponents of stent 10 are still situated in the catheter tip K, theradial forces developing upon the critical switching temperature beingexceeded and acting on the individual components of the stent 10 arestill compensated by the wall of the catheter tip K, so that—despite theactivation of the shape memory effect—the stent 10 is forcibly kept inits first (collapsed) shape.

Upon the subsequent manipulation of catheter tip K—by the appropriateincremental release of the stent 10—the individual components of stent10, are then discharged from the catheter tip K. As FIG. 3 a shows, thepositioning arches 15 a, 15 b, 15 c of stent 10 spread out radially dueto the acting radial forces. The expanded positioning arches 15 a, 15 b,15 c can then be positioned into the pockets T of the native cardiacvalve H.

Thereafter—as depicted in FIG. 3 b—the remaining components of stent 10are sequentially released from the catheter tip K. The releasedremaining components of stent 10, in particular the auxiliary arches 18a, 18 b, 18 c and the retaining arches 16 a, 16 b, 16 c with thevalvular prosthesis 100, then spread out radially and the valvularprosthesis 100 attached to the fastening portions 11 unfolds like anumbrella.

The radial forces acting on both the retaining arches 16 a, 16 b, 16 cand the auxiliary arches 18 a, 18 b, 18 c of the stent 10 as well as theradial forces acting on the upper end region 3 of stent 10, result inthe stent 10 being pressed radially against the vascular wall (cf. FIG.3 c). This effects a secure anchoring of stent 10 with the expandedvalvular prosthesis 100 at the site of implantation on the one hand and,on the other, a reliable seal of the valvular prosthesis 100 at thelower end 2 of stent 10.

The catheter tip K of the insertion catheter system is then manipulatedfurther to release the eyelets 24 of the stent 10, thereby allowing theupper end region 3 of the stent 10 to expand. In so doing, the valveleaflets of the native cardiac valve H are clamped between respectivepositioning and retaining arches and the valvular prosthesis 100disposed on the lower end 2 of stent 10 can spread open.

After the successful implantation of the stent 10 and valvularprosthesis 100, the catheter is then removed from the body of thepatient.

The invention is not limited to a stent 10 made from shape memorymaterial which self-expands from its first (collapsed) shape into itssecond (expanded) shape in response to an external stimulus. Rather, itis also categorically conceivable for the stent 10 to be expanded usinga conventional balloon system.

The inventive solution is also not limited to the embodiments asdescribed with reference to the attached drawings. Rather, combinationsof the specified individual features are also conceivable.

With respect to fixing the upper area 3 of stent 10 to the wall of theblood vessel into which the stent 10 is deployed, it would beconceivable for the stent 10 to comprise barb members arranged, forexample, on the eyelets 24, the tips of the barbs pointing toward thelower end 2 of stent 10.

LIST OF REFERENCE NUMERALS

-   1 endoprosthesis-   2 lower end of the stent/endoprosthesis-   3 upper end of the stent/endoprosthesis-   10 cardiac valve stent/stent-   11 fastening portion of the stent-   12 fastening holes-   13 upper end of the fastening portion-   14 lower end of the fastening portion-   15 a-15 c positioning arches-   15 a′, 15 a″ arms of the first positioning arch-   15 b′, 15 b″ arms of the second positioning arch-   15 c′, 15 c″ arms of the third positioning arch-   16 a-16 c retaining arches-   16 a′, 16 a″ arms of the first retaining arch-   16 b′, 16 b″ arms of the second retaining arch-   16 c′, 16 c″ arms of the third retaining arch-   17 first connecting web-   17 d upper end of the first connecting web-   17 p lower end of the first connecting web-   18 a-18 c auxiliary arches-   18 a′, 18 a″ arms of the first auxiliary arch-   18 b′, 18 b″ arms of the second auxiliary arch-   18 c′, 18 c″ arms of the third auxiliary arch-   20 head portion of the positioning arch-   21 reference marker-   22 connecting portion between the arms of neighboring positioning    arches-   23 catheter retaining means/catheter retaining head-   24 eyelet-   25 second connecting web-   100 valvular prosthesis-   101 thread-   102 flap segment of the valvular prosthesis-   H native cardiac valve-   K catheter tip of an insertion catheter system-   L longitudinal direction of the stent-   T pocket of the native cardiac valve

1-40. (canceled)
 41. An expandable stent comprising: a plurality offirst arches; a plurality of second arches, each second arch having anapex opposite an open end portion, the apex of each second arch beingaxially aligned, in a longitudinal direction of the expandable stent,with an apex of a corresponding first arch, and the open end portion ofeach second arch being joined to an open end portion of thecorresponding first arch; a plurality of third arches, each third archcorresponding to, and circumferentially interspaced between, twoadjacent second arches; and a valve prosthesis attached to a segment ofeach of the two adjacent second arches distal to the corresponding thirdarch.
 42. The expandable stent of claim 41, wherein each third archincludes an apex pointing in a proximal direction, and wherein the apexof each first arch and the apex of each second arch points in theproximal direction.
 43. The expandable stent of claim 41, comprisingexactly three first arches, exactly three second arches, and exactlythree third arches.
 44. The expandable stent of claim 41, wherein thesegment of each second arch defines a plurality of apertures.
 45. Theexpandable stent of claim 44, wherein each third arch is proximal to atleast one aperture defined by at least one of the second arches.
 46. Theexpandable stent of claim 41, wherein the apex of each first archincludes a radiopaque marker.
 47. The expandable stent of claim 41,wherein the open end portion of each second arch is joined to the openend portion of each first arch by a strut parallel to a longitudinalaxis of the stent.
 48. The expandable stent of claim 41, furthercomprising a plurality of head portions configured for removableattachment to a delivery device, each head portion connected to twoadjacent first arches by a strut.
 49. The expandable stent of claim 48,wherein each head portion defines an aperture.
 50. The expandable stentof claim 41, configured for implantation relative to a native valvecomprising a plurality of native valve leaflets, such that each firstarch is positioned within a corresponding pocket of the native valve ona first side of one of the native valve leaflets, and each second archis positioned on a second side of the native valve leaflet, each nativevalve leaflet being positioned radially inward of at least a portion ofthe plurality of first arches and radially outward of at least a portionof the plurality of second arches when the expandable stent isimplanted.
 51. The expandable stent of claim 41, wherein the stent isself-expandable.
 52. The expandable stent of claim 41, wherein eachsecond arch includes two apices opposite the open end portion of thesecond arch.
 53. An expandable stent comprising: a plurality of firstarches; a plurality of second arches, each second arch having an apexopposite an open end portion, the apex of each second arch being axiallyaligned, in a longitudinal direction of the expandable stent, with anapex of a corresponding first arch, and the open end portion of eachsecond arch being joined to an open end portion of the correspondingfirst arch, wherein the apex of each first arch and the apex of eachsecond arch points in a proximal direction; a plurality of third arches,each third arch corresponding to, and circumferentially interspacedbetween, two adjacent second arches and having an apex pointing in theproximal direction; and a valve prosthesis attached to each second arch.54. The expandable stent of claim 53, wherein the open end portion ofeach second arch is joined to the open end portion of each first arch bya first strut parallel to a longitudinal axis of the stent.
 55. Theexpandable stent of claim 54, further comprising a plurality of headportions, wherein each head portion is connected to two adjacent firstarches by a second strut.
 56. The expandable stent of claim 53, whereinthe valve prosthesis is sutured to each second arch through a pluralityof apertures defined by each second arch.
 57. The expandable stent ofclaim 56, wherein at least one aperture defined by each second arch isdistal to each third arch.
 58. An expandable stent comprising: aplurality of first arches; a plurality of second arches, each secondarch having an apex opposite an open end portion, the apex of eachsecond arch being axially aligned, in a longitudinal direction of theexpandable stent, with an apex of a corresponding first arch, and theopen end portion of each second arch being joined to an open end portionof the corresponding first arch; a plurality of third arches, each thirdarch corresponding to, and circumferentially interspaced between, twoadjacent second arches and having an apex pointing in the proximaldirection; a plurality of head portions at a distal end of theexpandable stent, each head portion defining an aperture; and a valveprosthesis attached to each second arch.
 59. The expandable stent ofclaim 58, wherein each head portion is connected to two adjacent firstarches by a strut.
 60. The expandable stent of claim 58, comprisingexactly three third arches.